A lithographic process includes the patterned exposure of a resist allowing portions of the resist to be selectively removed, thereby exposing underlying areas for selective processing, such as etching, material deposition, ion implantation and the like. Typically, lithographic processes utilize ultraviolet light for selective exposure of the resist. In addition, charged particle beams (e.g., electron beams) have been used for high resolution lithographic resist exposure. The use of e-beam based lithography systems allows for relatively accurate control of the electron beam at relatively low power and relatively high speed.
Electron-beam lithography has typically been limited to applications which do not require high throughput due to practical limitations, such as limitations on beam current. The maskless reflective electron beam lithography system utilizes a unique patterning transducer which partially overcomes these limitations and enables higher total currents and potentially higher throughput than was available in prior systems. Due to the high system throughput there is now a need for a high rate of pattern data flow since geometric data must be communicated to the electron-beam tool's print head, which becomes problematic as throughput increases. An additional feature of reflective electron beam lithography (REBL) is that the patterning transducer is maintained at elevated electrical potential, requiring pattern data to be transmitted to it over fiber optic links.
In raster-style electron-beam lithography systems, pattern data transmission has usually not employed data compression, as a bit-stream, in the case of binary beam-blanking, or a byte-stream, in the case of gray-tone blanking, has been sufficient to supply pattern data at the needed rates. However, in the REBL system, each digital pattern device (DPG) may consume pattern data at rates up to ˜0.5 terabyte/second, a high rate even by the standards of today's commercial telecommunications systems. Without data compression, REBL's data system would require a large number of optical fibers and fiber-optical components, making the packaging of these parts of the system ungainly and complex.
There are currently numerous general purpose compression methods. However, common methods involve decompression algorithms which are relatively complex, and as a result may not be suitable for ‘on-chip’ implementation in a system like REBL, whose patterning transducer (the dynamic pattern generator) consists of a CMOS chip in which numerous data streams must be simultaneously decompressed and which must therefore accommodate multiple copies of the de-compression circuit. Therefore, it is desirable to provide a method and system suitable for curing the defects of the prior art.